infoarena informatica de performanta

#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
int main()
{
int i,n=100;
char  sir[5], sir2[5], vocale[]="aeiouAEIOU";
printf ("Introduceti un sir: ");
scanf ("%s",sir2);
for (i=0;i<strlen(sir2);i++);
{
    if(sir2[i] == vocale)
    strcat(sir,sir2[i]);
}
printf("Ati tastat: %s \n",sir);
getch ();
return 1;
}